Bioreactors, often referred to as fermentors, are commonly used in bioprocessing. “Bioprocessing” refers to aerobic and anaerobic processes that involve microorganisms, e.g., cells, in a medium. Examples of bioprocesses include yeast fermentation, bacterial fermentation, cell culture, bacterial culture, and the production of a product using cells, e.g., using mammalian cells such as CHO cells to express a protein, e.g., a therapeutic protein, or an enzyme.
A bioreactor generally includes a vessel in which a bioprocess is carried out, and sensors and process controls that allow parameters of the process to be monitored and controlled. Bioreactors also typically include an agitator, for example a Rushton or marine impeller, that mixes the vessel contents during bioprocessing.
It is generally important to carefully control process parameters during bioprocessing, for example gas flow rates, temperature, pH, dissolved oxygen level, and agitation speed and conditions. Dissolved oxygen level is a measure of oxygen transfer from gas to liquid phase, which is important to many bioprocesses and can be difficult to accomplish. While oxygen transfer is generally helped by agitation, agitation speed is often limited by power consumption and in some cases the risk of damage to the microorganisms. In some cases, for example, in the case of mammalian cells, the microorganisms are fragile and may be sensitive to heat, shear, and/or other process conditions.